Which of the following is an unanswered question about life on earth?
a) how long has life existed on earth?
b) what were early forms of life like?
c) did early life arise spontaneously or did it come from space?
d) how does evolution occur?

Answer;

C) Did early life arise spontaneously or did it come from space?

Explanation;

-Many theories of the origin of life have been proposed, but since it's hard to prove or disprove them, no fully accepted theory exists.

-The answer to this question (Did early life arise spontaneously or did it come from space?) would not only fill one of the largest gaps in scientists' understanding of nature, but also would have important implications for the likelihood of finding life elsewhere in the universe.

you can't see the options

that is wrong, its not thymus.